Spatiotemporal Assessment of PM2.5 in Senior High Schools in Kumasi, Ghana using Low-Cost Sensors

Abstract Fine particulate matter (PM 2.5 ) poses significant health risks, particularly to children; yet, ambient air quality studies in school environments across Kumasi, Ghana, remain limited. This study utilized low-cost Airnote sensors and meteorological data (wind speed and wind direction) from the ERA5-Land Reanalysis to assess levels of PM 2.5 pollution across six senior high schools in Kumasi between 2022 and 2023, capturing spatial and seasonal variability during both the dry and wet seasons. Results revealed an annual median PM 2.5 concentration of 17.18 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> , exceeding the WHO annual guideline of 5 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> . Diurnal patterns exhibited bimodal peaks aligned with morning and evening commuting and domestic activities, driven by traffic emissions, biomass burning, and informal waste burning. Pollution levels were notably elevated during weekdays and Saturdays but lower on Sundays. Median concentrations were highest at SHS E (20.91 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ), followed by SHS A (19.22 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ), SHS F (18.16 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ), and SHS D (16.71 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ), while SHS B (15.32 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ) and SHS C (12.76 $$\mu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> g/m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>3</mml:mn> </mml:mmultiscripts> </mml:math> ) recorded the lowest levels. Seasonal differences were pronounced: the dry season showed significantly higher pollution (mean = 26.82 <jats:alt